Gratian. AE3. Siscia. 367-375 AD. 

DN GRATIANVS PF AVG, pearl diademed, draped, cuirassed bust right

SECVRITAS-REIPVBLICAE, Victory advancing left, holding wreath and palm. 
R in left field. 

Mintmark dot ASISC. 

RIC IX Siscia 15c, type x. Rare.